The present invention relates to piezo-electric crystal resonators in which the electrical field of excitation is produced in a direction parallel to one of their surfaces by electrodes, certain ones of which are located on this surface, and particularly but not exclusively, resonators having the form of a tuning fork.
Piezo-electric crystal resonators are very useful for forming the time base in many kinds of electronic apparatus and equipment, including clocks and watches. In many applications, crystal resonators in the form of a tuning fork have proved to be extremely advantageous, particularly in view of the possibilities of miniaturization which they offer. However, in the same type of application it equally is desirable to reduce as far as possible the consumption of energy required to maintain vibrations of the tuning fork, especially when the energy is supplied by batteries of very small dimensions in portable devices such as watches or pocket calculators. The resonator according to the invention is designed in such a manner as to reduce the consumption of energy by producing an excitation electrical field which is more homogeneous and locally more intense than those in the known resonators. Accordingly, the invention is applicable not only to resonators in which the crystal is in the form of a tuning fork, but also to resonators of all other forms, with a field of excitation parallel to a surface of the crystal which carries an excitation electrode.